Such sputtering cathodes are high-power sputtering cathodes and are also referred to as magnetron cathodes. Behind the target plate is disposed a magnet system, which generates on the opposing sputtering surface a closed magnetic tunnel in which the plasma of an ionized gas required for the sputtering process is enclosed. Thereby, on the one hand, the sputter rate is increased by the twenty to thirty-fold value compared to a magnet-free cathode, but, on the other hand, the energy density is focused onto a region beneath the magnetic tunnel and, consequently, also the erosion rate of the material of the target plate and the heat delivery into it. This forces a short-term change-out cycle of the target plate and an extremely efficient cooling system. The problems increase with the size of the sputtering cathode.
EP 0 476 652 B1 discloses closing off circular, relatively small cathode housings, in which are disposed magnet systems, with respect to the vacuum coating chamber through a relatively thick cathode plate (6 to 7 mm). Through this cathode plate and an encircling toroidal sealing ring the cathode housing, in which is disposed a cooling fluid flushing around the magnets, is closed off against the coating chamber. The patent expressly states that the penetration of the cooling fluid into the coating chamber leads to product rejects, since thereby the coating atmosphere—either inert gas or reactive gas—is spoiled. As the cooling fluid are specified for example water and ethylene glycol. The cathode plate can be implemented either homogeneously or laminated and be comprised of a base plate of aluminum, the target proper and a reinforcement layer of copper, optionally supplemented by a heating layer for outgassing the cathode before the coating. The stated cathode diameters reach up to 290 mm. However, a significant disadvantage is comprised in that in order to change the cathode plate, it is necessary to remove the cooling fluid, detach and clean the seal, before, after considerable loss of time, the system can again be taken into operation in the reverse direction.
The same document also discloses a base plate, in which, close behind the target material to be sputtered, closed cooling agent channels are disposed. However, here the hazard exists that if monitoring is neglected, the target material is etched through and the base plate is etched up to the cooling agent channels. This, in turn, entails the hazard of the cooling agent penetrating into the coating chamber. Means for establishing a connection of the cooling agent channels with the environment are not disclosed.
From DE 43 01 516 A1 is known a sputtering cathode of the above described species, in which a cooling agent channel is formed between an elastic diaphragm and a solid tub with an encircling hollow space and two encircling seals. Over the entire face of the diaphragm are disposed targets or target parts. The cooling agent channel and the target(s) are secured in place with alternatingly disposed screw connections from below and above, which, on the one hand, act via claws or nuts on the diaphragm with the tub and, on the other hand, onto the target margins. The magnets are here disposed outside of the cooling agent. However, since the entire sputtering cathode is disposed within a vacuum chamber (not shown), possibly leaking cooling agent could enter the vacuum chamber and negatively affect the coating process.
From DE 196 22 605 A1 and DE 196 22 606 C2 is known to dispose between the magnet system and the target plate at least one sheet metal blank of a magnetically conductive material in order to force onto the field lines, forming a magnetic tunnel for the plasma effecting the sputtering, a flatter course in order to widen the erosion trough in the target plate and to increase the [rate] efficiency of the material. In addition, DE 196 22 606 C2 also discloses a target base plate supporting the target.
The invention therefore addresses the problem of improving in a sputtering cathode of the species described in the introduction the heat transfer from target to cooling agent in simple, efficient, and cost-effective manner and to avoid the hazard of the cooling agent or its vapors penetrating into the vacuum chamber and of the impairment of the coating process.
The formulated problem is solved in a sputtering cathode of the species described in the introduction according to the invention thereby that
a) the supporting structure for the sputtering cathode comprises a hollow body, which is closed gas-tight against the interior space of the vacuum chamber and which connects the hollow space encompassing the magnet system with the atmosphere outside of the vacuum chamber,
b) the cooling agent channel is implemented as a conduit closed on its cross section periphery with at least one flat side, which [flat side] is in a thermally conducting connection with the diaphragm, and that
c) the diaphragm and the surfaces of the conduit facing away from the diaphragm, via said supporting structure are exposed to the atmospheric pressure obtaining outside the vacuum chamber.
Through the invention, in a sputtering cathode of the species described in the introduction, the heat transfer from target to cooling agent in simple, efficient and cost-effective manner is improved and the hazard of the cooling agent or its vapors penetrating into the vacuum chamber and the impairment of the coating process are avoided.
In the course of further embodiments of the invention it is especially advantageous if, either individually or in combination                the conduit for the cooling fluid has a rectangular cross section, whose one long side forms with the diaphragm a heat conducting connection,        the conduit for the cooling fluid is connected with the diaphragm through joining process,        the hollow body of the supporting structure is fastened on a mounting plate which is fastened on a wall of the vacuum chamber, which, within the connection site of the mounting plate, has an opening with respect to the ambient atmosphere,        at both ends of the conduit orthogonal tubular fittings are connected terminating in elbows, and from which connection lines are guided through the hollow body of the supporting structure up to the ambient atmosphere,        the supporting tub of the sputtering cathode via a support body closed on the periphery vacuum-tight is connected with the hollow body of the supporting structure,        the supporting tub of the sputtering cathode and the mountings for the target plate(s) are encompassed by a housing, which extends by means of a first frame over the mountings of the target plate(s) and by means of a second frame extends under the supporting tub up into the proximity of the support body and/or if        the conduit extends within the sputtering cathode approximately entrally between the different poles of the magnet system.        
In the following an embodiment example of the subject matter of the invention and its operational function and advantages will be explained in further detail in conjunction with a rectangular cathode according to FIGS. 1 to 6.